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We show that work can be extracted from a two-level system (spin) coupled to a bosonic thermal bath. This is possible due to different initial temperatures of the spin and the bath, both positive (no spin population inversion) and is…

Quantum Physics · Physics 2009-11-10 A. E. Allahverdyan , R. Serral Gracia , Th. M. Nieuwenhuizen

Measurement and feedback allows an external agent to extract work from a system in contact with a single thermal bath. The maximum amount of work that can be extracted in a single measurement and the corresponding feedback loop is given by…

Statistical Mechanics · Physics 2024-01-19 L. Dinis , J. M. R. Parrondo

We analyze an autonomous thermoelectric engine composed of two superconducting qubits coupled to separate heat baths and connected by a Josephson junction. Work and heat are process quantities and not observables of the engine quantum…

Quantum Physics · Physics 2020-01-22 Katerina Verteletsky , Klaus Moelmer

Work extraction in quantum finite systems is an important issue in quantum thermodynamics. The optimal work extracted is called ergotropy, and it is achieved by maximizing the average work extracted over all the unitary cycles. However, an…

Quantum Physics · Physics 2024-04-10 Gianluca Francica , Luca Dell'Anna

Quantum states that can yield work in a cyclical Hamiltonian process form one of the primary resources in the context of quantum thermodynamics. Conversely, states whose average energy cannot be lowered by unitary transformations are called…

Quantum Physics · Physics 2016-11-17 Eric G. Brown , Nicolai Friis , Marcus Huber

We introduce quantum information engines that extract work from quantum states and a single thermal reservoir. They may operate under three general conditions: i/ Unitarily Steered evolution (US); ii/ Irreversible Thermalization (IT) and…

Quantum Physics · Physics 2014-03-21 J. M. Diazdelacruz , M. A. Martin-Delgado

Work extraction is one of the most central processes in quantum thermodynamics. However, the prior analysis of optimal extractable work has been restricted to a limited operational scenario where complete information about the initial state…

Quantum Physics · Physics 2025-02-14 Kaito Watanabe , Ryuji Takagi

Photon emission by tunneling electrons can be encouraged by locating a resonator close to the tunnel junction and applying an appropriate voltage-bias. However, studies of normal metals show that the resonator also affects how the charges…

Mesoscale and Nanoscale Physics · Physics 2019-08-29 W. T. Morley , A. Di Marco , M. Mantovani , P. Stadler , W. Belzig , G. Rastelli , A. D. Armour

We analyze work extraction protocols using the long-lived quantum coherence of a three-level quantum system, which is coupled to a thermal bath through dipole-monopole interactions. We identify situations where persistent quantum coherence…

Quantum Physics · Physics 2025-08-05 Wenjing Chen , Si-Wei Han , Xiaoshan Feng , Jun Feng

In quantum systems which satisfy the hypothesis of equal weights for eigenstates [4], the maximum work principle (for extremely slow and relatively fast operation) is derived by using quantum dynamics alone. This may be a crucial step in…

Statistical Mechanics · Physics 2007-05-23 Hal Tasaki

Colloidal heat engines extract power out of a fluctuating bath by manipulating a confined tracer. Considering a self-propelled tracer surrounded by a bath of passive colloids, we optimize the engine performances based on the maximum…

Statistical Mechanics · Physics 2018-05-17 D. Martin , C. Nardini , M. E. Cates , É. Fodor

Quantum coherence, encoded in the off-diagonal elements of a system's density matrix, is a key resource in quantum thermodynamics, fundamentally limiting the maximum extractable work known as ergotropy. While previous experiments have…

Quantum Physics · Physics 2025-12-04 Li Li , Silu Zhao , Yun-Hao Shi , Kai Xu , Heng Fan , Dongning Zheng , Zhongcheng Xiang

We discuss work extraction from classical information engines (e.g., Szil\'ard) with $N$-particles, $q$ partitions, and initial arbitrary non-equilibrium states. In particular, we focus on their {\em optimal} behaviour, which includes the…

Statistical Mechanics · Physics 2020-09-10 Léo Touzo , Matteo Marsili , Neri Merhav , Édgar Roldán

We consider the task of extracting work from quantum systems in the resource theory perspective of thermodynamics, where free states are arbitrary thermal states, and allowed operations are energy conserving unitary transformations. Taking…

Quantum Physics · Physics 2013-02-13 Paul Skrzypczyk , Anthony J. Short , Sandu Popescu

Inspired by the primary goal of quantum thermodynamics -- to characterize quantum signatures and leverage their benefits in thermodynamic scenarios -- , we design a work extraction game within a bipartite framework that exhibits a quantum…

Quantum Physics · Physics 2025-09-15 Tanmoy Biswas , Chandan Datta , Luis Pedro García-Pintos

We consider locally thermal states (for two qubits) with certain amount of quantum entanglement present between them. Unlike previous protocols we show how work can be extracted by performing local unitary operations on this state by…

We consider overdamped Brownian particles with two degrees of freedom (DoF) that are confined in a time-varying quadratic potential and are in simultaneous contact with heat baths of different temperatures along the respective DoF. The…

Statistical Mechanics · Physics 2024-06-21 Jordi Ventura Siches , Olga Movilla Miangolarra , Tryphon T. Georgiou

The optimal efficiency of quantum (or classical) heat engines whose heat baths are $n$-particle systems is given by the information geometry and the strong large deviation. We give the optimal work extraction process as a concrete…

Quantum Physics · Physics 2017-07-19 Hiroyasu Tajima , Masahito Hayashi

Maximum quantum work extraction is generally defined in terms of the ergotropy functional, no matter how experimentally complicated is the implementation of the optimal unitary allowing for it, especially in the case of multipartite…

Quantum Physics · Physics 2025-01-27 Riccardo Castellano , Ranieri Nery , Kyrylo Simonov , Donato Farina

Free energy fixes the maximum work of a thermodynamic process once the state and Hamiltonian are specified. A work-extraction task asks a different question: how much average work can a single device realize across several preparations and…

Quantum Physics · Physics 2026-05-06 Sumit Rout , Aravinth Balaji Ravichandran , Paweł Horodecki , Anubhav Chaturvedi